Even when a pneumatic tire goes flat, a number of technologies, which enables the tire to make an emergency run for a reasonable amount of mileage, have been proposed in response to the market demanding such a technology as above. Among the thus proposed technologies, there is a technology which realizes run-flat traveling in a manner that, with a core being mounted on a rim inside a cavity portion of a pneumatic tire, the pneumatic tire in a deflated condition is supported by the core (for example, refer to Patent Documents 1 to 3).
A run-flat support member as described above is formed of a configuration: which includes an annular shell formed in a structure with legs astride which, while having an abutting portion projected on an outer peripheral side of the structure, has legs along both sides of the abutting portion, the abutting portion being intended to abut an inner surface of a tire; and where elastic rings are respectively fixed to these legs. The run-flat support member is intended to be mounted on the rim through the elastic rings. According to this run-flat support member, the run-flat support member can be used, substantially without adding any particular modifications to existing wheel and rim, with the existing wheel and rim as they are, and hence have an advantage that it can be made acceptable to the market without bringing any serious confusion to the market.
When the above run-flat support member is mounted onto a tire wheel assembly, it is necessary to insert the run-flat support member in a cavity portion of a pneumatic tire at first, and then to perform rim assembling work of the pneumatic tire in a state where this run-flat support member is contained therein. For this reason, for the purpose of facilitating the rim assembling work, it is desired that the elastic rings of the run-flat support member easily go over rim flanges, that is, inner diameters of the elastic rings be as large as possible. However, if the inner diameters of the elastic rings are made uniformly large, there arises a problem that the mounting of the run-flat support member becomes unstable.
[Patent Document 1] Japanese patent application Kohyo publication No. 2001-519279
[Patent Document 2] Japanese patent application Kokai publication No. 2001-163020
[Patent Document 3] Japanese patent application Kokai publication No. Hei10-297226